1. Field of the Invention
The present invention is generally directed toward nuclear magnetic resonance (“NMR”) and is more particularly directed toward high precision elemental composition determination using NMR.
2. Related Art
Measurements of the concentration of various elements are valuable in a number of industrial situations. Examples include the characterization of the elemental content of raw materials or feedstocks, the monitoring of concentrations in various stages of material or chemical processing, the certification of elemental content of finished products, and the verification of product quality by downstream customers. The elemental concentration measurement usually needs to be cost effective, precise, rapid, robust, straightforward and flexible in order to provide maximal economic benefit. In some cases, the measurement must be minimally or non-invasive and non-destructive.
A number of analytical chemistry techniques are used for elemental analysis and concentration determination. Techniques based on inductively-coupled plasma sample decomposition, followed by detection with mass spectrometry, atomic emission spectroscopy, or other methods are common. Flame-based atomic emission spectroscopy or atomic absorption spectroscopy may also be used. Classical wet chemistry methods may be employed, including precipitation, titration, or other approaches. Separation techniques such as gas chromatography, liquid chromatography, or capillary electrophoresis may be employed. Nuclear magnetic resonance spectroscopy may also be utilized for certain elements.
The currently available solutions for measuring elemental concentration all fail to meet one or more of the requirements of cost, precision, speed, robustness, simplicity, and flexibility. For nearly all of them, the sample to be measured must be prepared carefully by a technician, usually in a wet chemistry laboratory. The accuracy relies heavily on multipoint calibration curves and may nevertheless be limited even under ideal measurement conditions. Complicated procedures limit the practically achievable measurement precision. Some techniques, such as conventional NMR, may be considered ill-suited for high precision determinations and may be used mostly for qualitative analysis. Some instruments or procedures may be limited to a single chemical element, or a small number of elements, when the need exists for multi-element characterization. The cost per measurement may be high due to capital equipment and siting expenses, the cost of consumables, maintenance costs, and the technician's time. The measurement procedure may take too much time to provide effective feedback to operational decisions and control. Similarly, the measurement facility may be too far removed from the operational facility to allow for effective integration of process and characterization. Variations between samples, or between technicians, may cause the measurements to fail to meet accuracy requirements. The devices and methods used may fail to meet the desired performance specifications under non-ideal factory or field conditions, or the devices may not be capable of being moved to or being operated in the locations where the measurements need to be made. This lack of flexibility, or the failure to meet other requirements of cost, precision, ease of use, measurement speed, integrability with other processes, and robustness can undermine the desired application of any of the currently available elemental concentration determination methods.
Therefore, what is needed is a system and method that overcomes these significant problems found in the conventional systems as described above.